Space enclosures having a domelike structure were generally developed to combine the desirable properties of a tetrahedron and a sphere and frequently took the form of a geodesic dome. Those constructions utilized a basic skeletal arrangement for supporting a surface covering. The framing system commonly employed a geometric network of rod elements, tubular members or struts joined at their ends by a hub or socket-node with rigid or flexible surface panels placed over that triangulated framework. A shortcoming of those dome structures was that they relied exclusively on the hubs and struts for structural rigidity. A further problem was that the hubs which connected and held the ends of the struts were subject to concentrated multiple directional forces and thus had a greater potential for stress failure both as a result of material fatigue and because of the unusual load conditions.
Another dome construction of the prior art provided for direct connection of adjacent panel edges without an underlying framework as typically illustrated in U.S. Pat. No. 3,740,903. It should be observed, however, that those systems of pre-assembly panels did not utilize surface panels as load transfer members but rather relied upon peripheral flanges which extended along the margins of each panel and functioned in a similar manner as the aforementioned skeletal framework.
Still another variation of the previous dome constructions included panel members wherein the abutting edges were interlocked such as shown in U.S. Pat. Nos. 4,180,950 and 4,287,690. A distinct limitation of those last mentioned constructions concerned the strict tolerance requirements for the precise interfitting of the panels and the inherent problems in the erection of those structures. Furthermore, all of the devices as previously discussed did not incorporate a support arrangement having two interrelated structural surfaces.
The U.S. Pavilion at Expo '67 in Montreal, Canada employed a double layer space frame to form a three-quarter sphere, double grid geodesic dome. That structure however, as illustrated in the publication, Geodesics by Edward Popko, .COPYRGT.1968, University of Detroit Press, in Fig. No. 88, consisted of a hexagonal inner layer and triangulated outer layer with a web network of tubular members joining the two layers. That geodesic dome did not use rigid surface panels as structural components.
The present invention in contrast, is derived from a topological approach to geometric forms which provides the basis for the relationship between structural incorporated surfaces.